船舶調査から推定した日本周辺におけるアホウドリの海上生息域

Abstract

The pelagic distribution of the Short-tailed Albatross Phoebastria albatrus in the western North Pacific o# the Nansei Islands to eastern Japan was examined from data collected by research vessels from 1999 to 2004. Fifteen groups and 325 individuals of Short-tailed Albatrosses were recorded during line-transect sighting surveys, and 25 groups and 45 individuals were recorded in opportunistic observations during cruising, drifting and experimental fishing. Results of the sighting survey revealed that Short-tailed Albatrosses appeared in three areas o# Japan from the fourth quarter to the next second quarter: 1) o# the Pacific coast of eastern Japan, 2) near Torishima of the Izu Islands, and 3) near Minamikojima of the Senkaku Islands. Geographical analysis of the occurrence points showed that large numbers of Short-tailed Albatrosses aggregated in the near-shore waters within 30 km of the breeding islands, and that they also utilized the Kuroshio Oyashio mixture zone above the continental shelf edge and slope 2001400 m in depth and 2070 km o#shore of the Pacific coast of eastern Japan. Results of this study suggest that ar esting area near the breeding islands and a foraging area above the continental slope o# eastern Japan are important marine habitats for the Short-tailed Albatross during the breeding period.